Method of and apparatus for subjecting fluid matter to a high-frequency electric field



R. A. BIERWIRTH METHOD OF AND APPARATUS FOR SUBJECTING FLUID May 23, 1950 MATTER TO A HIGH-FREQUENCY ELECTRIC FIELD Filed Sept. 28, 1944 //V 777KB in 11v VEN TOR. m/wmwfifl/mw/er/f BY 1 E ATTORNEY Patented May 23, 1950 -METHD OF" AND APPARATUS FOR SUB- JECTING FLUID MATTER TO A HIGH-FRE- iQUENCY; ELECTRIC FIELD Rudolph Bierwirth, Princeton, N. .J., assignor to Radio Corporation ofAmerica, a-oorporation of Delaware zApplication September 28;? 1944, Serial No.- 556,265

3" Claims. 11 This invention relates to improvements. in. the earn of. subjecting milk;-and..other liquid .or fluid ematter. to an .electricfield.

v It has; previously been proposed to vgenerate 1. ,tinuousflow. method of theprior. art may .exhibit a burnt taste, while more or less tacky materials .suchas latex, essential .oils (e. g., orange juice) and certain polymeriz'able plastic materials, when sanvelectriefieldof a desired frequencyand inthus treated, may form an adherent coating on ..tensitylwithin a.-..glass..or other dielectric conthe innerwalls of the conduitadjacent to the -:duit-.(as .by meansoiwspacedapart. electrodes electrodes through which the radio frequency .izmountedion-oradjacenttothe walls of theconenergy is. applied. ,-duit). andto. flow the materiallto/ be treated. at Accordingly, the principal object of .the present ra-certain rate,:throughthefieldwithin theconinventionisto provide a new, and improved fcon duit with a view to heating saidmaterial to the tinuous flow method of subjecting mill ,.orange .degree-required .tosterilize,..condense crotherj'uice,.beer, latex landnumerous other fluid or .uwisealter its contents or. its physicalor chemical fluent materials to an electricfield, and one astructure. which in its-practice obviates theforegoing and ..The,. principal .problem encountered .in the v other lessapparent objections toprior art methpractice of.,such ffcontinuousfiow. methods of odsof treatingsuch materials.

treating fiuid materials with-an electric fieldis Another and relatedobjectoi thepresent inthat of preventing localized .oyerheating of. the vention is to provide an improved and. inexpen-- .imaterial and many ingenious..electrodearrangesive method of and apparatus .for subjecting the rmenta puniping-systemsuand thermally. actuated 20, entire cross-sectional area of a fluid streamuniigcontrol-.valveshave .been designed with-a view formly to the action. of an electric field.

-.toso1ving1.this problem. .:All-suchprioriartsya .The foregoing and other objects are achieved tems, however, appearntouloesbased upon the in accordance with the invention by generating ;seemingly,plausible,-but;actually. erroneous,-asan electric field in the space between. one or ...sumption-.that-ifthe.Jdistributionand intensity more pairs of capacitor electrodes and'causing of the lines of force withinthe conduit. areiof theliquid or the'fluent material to pass through .-r.a.desired,-.pattern and. value, it is thenmerely said fieldin the form ofa continuous jet, spout ...-necessary.,to. flow.acertainvolume .ofimaterial 'or"s0lid stream. In accordance with the in- ..throughthe .conduitina given. period of time vention, the stream of material in passing through inordertoachieve the desired result. 3 the electric field moves with substantially uni- .,.The ,.r.eason iwhy vlocalizedoverheating..may form velocity (as measured along across-secioccur in spiteiottheelaborate. precautions herevtional areaof the stream) and is subject only to xtoforeemployed toprevent such .overheatinggiis that substantiallynegligible degree of frictional that--.a..fiuid. stream.infiowingthrough a pipe retardation providedloy the air or other gaseous noraconduitisi-subjectedlto diiierent degrees of ambient surrounding the stream; thusnopart ;,frictional retardationes measured along a line of the. cross-sectional .area of the stream is .,,.normal to...thefdirection. oftrav'el ofthe stream. .slowed down '(as in the prior'art) by positive .ilhus, it .canbe demonstratedjthat'the.molecules "frictional contact with the walls of a conduit or ..or. otherelementary.particles which in' their flow other container. 1 contact theinner surface .of the conduit are sub- .In order to furtherensure that each molecule .je'ct.,to a greater degreeof frictional retardation or other elementary particle of theiiuid material "thanthe particles whichmake upthe center or willfbe subject "to the field for the same period core. ofl.the. stream. 'Themolecules or otherfiuofltime. as theothers, means are 'prefera'blyproent particles which are thus retarded may revided for minimizing the possibility of. turbulence main, by reason'r'ofrtheir relatively low velocity, in .thestream of material being treated. within the electric field for a period of time sub- Certain preferred details "oi"; construction and ""stantiallyionger than required "to raise their operation will be apparent-and the'invention ittemperatures to the degree calculatedtoefiect self will behest understood by'reference' to the the desire'd'physicaPorchemical. change in the "following specification and 'toithe accompanying material, and it is this prolonged exposure to the 59 drawing, wherein .-"-e1ectric.field of only a portioniof the.material jEigure' 1-..is a partly diagrammatic elevationai -r.:; thatfresults in'" localized overheating. View .of an apparatus constructed inaccoidance Localized overheating is manifest indifferent with the principle of the invention for theelecways in different materials. Thus, milk pas trical treatment of various fluid materials, teurized with radio frequency energy by the con- Figure 2 is a sectional view taken on the line IIII of Fig. l and shows one form of screen for preventing turbulence in the fluid stream, and

Figure 3 is a View similar to Fig. 1 but showing an alternative embodiment of the invention.

In the embodiments of the invention which have been selected for illustration, 1 designates generally a reservoir for the liquid or fluid material to be treated, and 3 designates means in the form of a circular pipe or nozzle for causing the material to flow downwardly from the reservoir in the form of a continuous jet or stream 5. When (as described in application Serial No. 556,264 of George H. Brown, filed concurrently herewith) the apparatus here illustrated is to be used in the pasteurization of milk, or other liquid, the said liquid may be preheated. Ordinarily the velocity of the jet will be determined by the force exerted upon the column of liquid in the pipe 3 by the body of liquid in the reservoir I. However, an auxiliary pump (not shown) may be provided for regulating the velocity of the jet whenever necessary or desirable.

In order to minimize any turbulence in the stream 5, the liquid may be caused to pass through a foraminous surface such as the metal screen I (see Fig. 2) mounted Within the pipe adjacent to the lower end or outlet of the said pipe. The material thus emerges from the said outlet in the form of a continuous, non-turbulent, "solid stream or jet of uniform cross-sectional area and this uniformity in the flow and dimensions of the stream is maintained (without the use of any retaining walls) over a distance suiilcien'tly long to permit the application of a high frequency electric field to the said stream. The energy for creating the electric field is supplied by an oscillator 9 and is applied to the stream by a pair of spaced apart electrodes M, iii (Fig. 1); 2!,23 (Fig. 3).

The electrodes H and I3 of Fig. l comprise a pair of curved metal plates arranged in capacitive relation on opposite sides of the stream, with the inner concave surfaces of the said plates presented across an intervening space I5 to the circular surface of the stream. If de sired, however, the pipe or nozzle 7 may be so designed that the fluid emerges therefrom in the form of ribbon made up of one or more jets, in which case the elctrooles may comprise a pair of flat metal plates (not shown) arranged opposite each other and parallel to the major surfaces of the ribbon. In any event, the intervening space l5 need be no wider than necessary to prevent accidental contact with the material of which the said stream or streams is comprised.

The electrodes 2| and 23 of Fig. 3, on the other hand, comprise a pair of metal bands or ribbons which encircle the stream 5 and are mounted one above the other in collinear and symmetrical capacitive relation, on the outer surface of a glass tube 25 which has an inside diameter substantially larger than the diameter of the stream 5 which passes therethrough. The tube 25, in addition to comprising a convenient support for the electrodes 25 and 23, also serves as a shield for protecting the stream or jet 5 against any turbulence in the air or other gaseous medium through which the stream passes and which might tend to alter the path, contour or dimensions of the stream. As here shown. the tube 2.":v is provided at its lower end with a bulbous portion 21 into which the now treated material is received. In the embodiment of the invention shown in Fig. 1, a funnel 29 is provided for the same purpose.

It will be appreciated by those skilled in the art to which this invention appertains that, al though the direction of the lines of force which comprise the alternating electric field between the electrodes is different in the two illustrated embodiments of the invention, the stream 5 is affected in the same manner in each case, i. e., the material of which the streams 5 are comprised becomes heated to a degree determined by the frequency and intensity of the electric energy applied to the stream by the said electrodes. The invention is of course not limited to the ise of alternating currents of any particular frequency or power, as these factors depend to a large extent upon the nature of the material being processed, and the time it requires for a particular treatment. However, it may here be mentioned that with the electrodes arranged in the manner shown in Fig. 3 and supplied from a 2 kilowatt oscillator with energy of a frequency of the order of 30 megacycles per second, the apparatus operated to raise the temperature of jet of milk from about 140 F. to about 205 F. in a period of time considerably less than one second, and this, too, without causing the milk to exhibit the burnt taste characteristic of milk treated under similar conditions, but with its flow retarded, as in the prior art, by contact with the inner walls of a conduit.

It will now be apparent that the present invention provides a novel method of and means for subjecting all of the molecules or other elementary particles comprising a liquid or fluent stream uniformly to the action of an electric, or an electromagnetic, field.

What is claimed is:

1. A method of treating a liquid which comprises: causing said liquid to move along a path throughout at least a portion of which said liquid is unconfined at its boundaries, and subjecting said liquid to the influence of a high frequency electric field only during its passage along that portion of said path whereat said liquid is unconfined at its boundaries.

2. A method of treating fluid matter which comprises: causing said fluid matter to flow in the form of a stream along a path throughout at least a portion of which said stream moves at a substantially uniform velocity as measured across said stream, and subjecting said stream to the influence of a high frequency electric field only 3 during its passage along said portion of said path.

3. In apparatus for the treatment of fluent matter with an electric field, a conduit constituted of a dielectric material, a pair of electrodes mounted in spaced capacitive relation on the outer surface of said conduit, and means for projecting said fluent matter through the bore of said conduit between said electrodes and out of contact with the inner surface of said bore.

RUDOLPH A. BIERWIRTH.

REFERENCES CITE!) The following references are of record in the file of this patent:

UNITED PATENTS Number Name Date 1,934,704 Golden Nov. 14, 1933 2,303,341 Dufour et a1. Dec. 1, 1942 

